•Epoch
of Recombination:
–Redshift
about z=1500 radiation temperature was some 4000 K, and
enough ionizing photons (just in the Wien region of
the spectrum, but enough since many more photons
than baryons) to keep hydrogen ionized. See text calculation, or do it yourself.
–Epoch
of recombination defined to be redshift for which 50% of
the H is ionized.
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